ForwardTracker::Stringer Node1 ForwardTracker::Stringer + Stringer() + operator()() + str() Node2 std::shared_ptr< std ::stringstream > + operator->() Node2->Node1 -m_ost Node3 std::stringstream Node3->Node2 +ptr Node4 std::basic_stringstream < char > Node4->Node3 Node5 std::basic_iostream < Char > Node5->Node4 Node6 std::basic_istream < Char > Node6->Node5 Node9 std::basic_ostream < Char > Node9->Node5